In the last decade, several nanometric filamentary structures have been synthesized. In fact, the interest for these one-dimensional structures has considerably grown. Several efforts and progress have been made in the synthesis, property characterization, assembly and applications of these one-dimensional structures. Some of these recent developments have been reported in (J. Liu, S. Fan and H. Dai, J, MRS Bull. 24 (2004), 244; J. Sloan et al., MRS Bull. 24 (2004), 265; Walt A. de Heer, MRS Bull. 24 (2004), 281; Y. Xia et al., Advanced Materials 15 (2003), 353.), which are hereby incorporated by reference in their entirety. However, there is still room for improvement in the proposed methods. Since many of these nanometric filamentary structures can be particularly volatile, they are difficult to deposit or recover without loosing at least a portion of them. Up to now, the deposition of nanometric filamentary structures has mostly been realized by thermophoresis. Such a technique generally requires large water-cooled surfaces, acting as collector of the product. Such a technique is not optimized for a large-scale production and often results in a deposit having a powder or membrane form that is relatively difficult to recover. It would therefore be desirable to be provided with a method and apparatus that would prevent such drawbacks.
Among these one-dimensional nanometric filamentary structures, carbon nanotubes have demonstrated very interesting properties. Carbon nanotubes are available either as multi-wall or single-wall nanotubes. Multi-wall carbon nanotubes have exceptional properties such as excellent electrical and thermal conductivities. They have applications in numerous fields such as storage of hydrogen (C. Liu, Y. Y. Fan, M. Liu, H. T. Cong, H. M. Cheng, M. S. Dresselhaus, Science 286 (1999), 1127; M. S. Dresselhaus, K. A Williams, P. C. Eklund, MRS Bull. (1999), 45) or other gases, adsorption heat pumps, materials reinforcement or nanoelectronics (M. Menon, D. Srivastava, Phy. Rev. Lett. 79 (1997), 4453). Single-wall carbon nanotubes, on the other hand, possess properties that are significantly superior to those of multi-wall nanotubes. For any industrial application such as storage or material reinforcement, the amount of single-wall carbon nanotubes produced must be at least a few kilograms per day. A difficulty encountered with the synthesis of single-wall carbon nanotubes, especially for their recovery, is that they are very volatile and they can be lost during the synthesis. By using the known methods of producing single-wall nanotubes, a powder or membrane form is obtained and large flows of cooling fluid are required in order to deposit the nanotubes carried in the gas.
In the methods and apparatuses that have been proposed so far for producing nanometric filamentary structures, there is no proposed solution that is efficient in order to determine the quality and/or quantity of the produced structures during the synthesis, In fact, such an analysis is made only when the production is stopped. There is thus no reliable way, during a synthesis, to determine if a given amount of structures already produced is getting contaminated with structures of poor quality. There is also no reliable way to determine if the efficiency of the production (i.e. the quantity of structures produced) is maintained during all the process or if it is lowered or considerably diminished at a certain time.
With respect to the synthesis of nanometric filamentary structures, many methods have been proposed in which the structures are deposited on a cooled surface such as a metallic plate. However, when using such methods, it results in the formation of a powder and large flows of cooling fluid are required. In fact, several types of nanometric filamentary structures have tendency to be fine powder or membranes compounds that are complicated to recover and have also tendency to be dissipated in the air.
U.S. Pat. No. 6,899,945 describes a three-dimensional single-wall carbon nanotube solid block material so-called buckyrock material. Such a material is described as being very solid, rigid and generally inflexible, and effective for use in armor. This document describes that such a material has a density of 0.7205 g/cm3.
U.S. Pat. No. 6,979,709 describes a macroscopic carbon fiber comprising at least about 106 single-wall carbon nanotubes bundled together in generally parallel orientation. The single-wall carbon nanotubes are arranged in a regular triangular lattice, i.e. in a close-packed structures. Such a macroscopic carbon fiber is obtained by a growth technique in which the hemispheric fullerene cap is removed from the upper ends of the tubular carbon molecules in the array, and the upper ends of the tubular carbon molecules in the array are then contacted with a catalytic metal. A gaseous source of carbon is supplied to the end of the array while localized energy is applied to the end of the array in order to heat the end to a temperature in the range of about 500° C. to about 1300° C. The growing carbon fiber is continuously recovered.
Another major drawback in the synthesis of carbon nanotubes is that the methods that have been proposed so far are not continuous. In fact, to obtain a continuous method for producing carbon nanotubes, the synthesis and the deposition and/or recovery must be carried out in a continuous manner.